Chinese scientists and surgeons have been at the forefront of 3D printed medical applications over the last few years, and regular readers will have doubtlessly noticed a lot of 3D printed components being used in surgeries in Chinese hospitals. And last week, we learned that this number is doubtlessly set to skyrocket, as China's Food and Drug Administration announced that China's self-developed 3D printed hip replacement (joint) has been commercially certified, and is set to be put to large-scale clinical use. Now, new reports are coming in about how remarkable these 3D printed titanium acetabular cups, that have been formally approved for use in China, actually are and how they are made; among others, they will be more affordable, easier to manufacture, will last longer and reduce the risk of subsequent complications.

To refresh your memory, the approved 3D printed hip joint prosthesis was developed by Dr. Zhang Ke, Liu Zhong Jun, and Cai Hong of Peking University Third Hospital in cooperation with AK Medical, a Chinese private medical company. The 3D printer used in the manufacturing of the hip joint was designed by a Swedish company Arcam AB and uses the Electronic Beam Melting (EBM) method of manufacturing, a more precise method than laser sintering and one used by NASA for various experiments.

This is good news for the aging Chinese society, where hip disease and other issues (necrosis, dysplasia, fractures, and bone diseases such as arthritis) necessitating hip replacement is becoming more and more common. As dr. Zhang Ke recently pointed out, joint replacement surgery is very common in China – about 400,000 took place in 2014, of which at least two thirds is specifically focused on hip replacement. Depending on the domestic or imported artificial joints used, an operation costs about 50,000-100,000 RMB, something many families cannot afford. A domestically-made traditional prosthesis is often not satisfactory.

The imported hip alone quickly costs around 30,000-40,000 RMB, with high-end imported products in the 60,000-80,000 RMB range. ‘We have used quite a lot of imported products, as imported products accounted for 70% of the market, especially in the Beijing, Shanghai, and Guangzhou areas more than 90% are imported, something not everyone can afford,’ Cai Hong explains. Part of this problem is that foreign companies have begun merging with Chinese businesses over the last 5-8 years, gradually forming a market monopoly with higher prices. Zhang Ke estimated that 70% of a patient’s money goes to the imported part alone. Both predict that 3D printing can reduce that price by a third or even half. Breaking the monopoly with 3D printing should also reduce other prices.

The acetabular cup is the component which is placed into the acetabulum (hip socket), Left: 3D printed cup, right: domestic made cup.

So how does this 3D printed innovation help them? Well only the acetabular cup in the entire artificial hip is 3D printed, with the rest not being so very different. The hip prosthesis is composed of four parts: a ceramic femoral head, a femoral stem, an acetabular cup, and apolyethylene insert. The currently used ceramic head is made in Germany, the stems come from the United Kingdom, only the Cup is manufactured by 3D printers. Deputy Director at the hospital Cai Hong explains, the acetabular cup is manufactured by the most advanced 3D metal printing technology. In the past, the cup was made through titanium alloy casting, and needed to be melted into liquid and poured in the mold of titanium alloy and then cooled down to form a shape. A micro-porous coating was then added the surface.

But this takes two steps to manufacture, while 3D printing only requires one. Doctors send data to the manufacturing enterprise, where an engineer builds 3D models with it. Using direct metal laser sintering technology, the laser beam fuses the titanium powder into a solid form. Layer by layer, the 3D printer tranforms titanium alloy powder into cups with micro-hole structure, and dozens of cups can be made in a single sitting. This far more effective method was born in 2009 when, by chance, Professor Zhang Ke and doctor Cai Hong went to Sweden for an academic meeting and encountered a metal 3D printer. From his long-term clinical experience in the medical field, Zhang Ke realized that it can be widely used in medical applications. After returning to China, he received support from Liu Zhongjun, Director of the bone department at the Beijng University Third Hospital. For the next step, Zhang Ke began leading the Group of Orthopedic Joints team to develop the first Chinese 3D printed hip products.

However, as tests revealed, 3D printing does more than reduce prices. Just a few weeks ago, Cai Hong’s office replaced an existing Chinese-made artificial acetabular cup with a 3D printed one. The patient in question was Wang Xiulan from Shandong Province. She walked around with the earlier model for five years, which were all just agony. Although screwed to her hip, the parts prevented the bones from growing together again. The screws loosened, causing the cup to rub against contact surface continuously, causing horrendous pain.

‘Only when the bones grow into the Cup it can be permanently fixed, otherwise will only be a temporary fix,’ Cai Hong explained after leading the revision surgery which cost the patient another 100,000 yuan (after paying 40,000 for the previous surgery). The difference is that the common cast cup has a smooth surface, while the 3D printed version is rough and covered with small holes. This structures mimics that of human bones and increases stability while providing a good environment for regrowth. Not only is the risk of loosening reduced, in the future custom printing will ensure a perfect fit. So far, dozens of patients have received 3D printed hip replacement surgery, and ‘all the clinical results were very good, we did not see the loosening of prosthesis, displacement and failure conditions yet,’ Cai Hong said.

And as he went on to explain, these hips also last very long. ‘Current international standards requires that at least 90% of people can use a replacement for more than 10 years, and 80% can use one for more than 20 years. However, 3D printed hip replacement can be used for at least 20 years,’ he says.

While this is all good news, we can expect more in a few years from now. Plans already exist for 3D printed artificial vertebral bodies and axis, among others, but that will take a while. Currently, the artificial vertebral body has entered the stage of clinical examination; while the 3D printed axis is at the clinical trial stage. This will take quite a bit longer than with the hip replacements, as they were able to entirely skip the clinical trials in China because imported similar products had already been approved and already used in Korea and Germany, Cai Hong explained. ‘China's 3D printing implant registration and approval process is relatively long; to get our research and development of artificial hip joints from clinical research finally approved took 40 months,’ he says, though he hopes it can be shortened this time.

Also problematic is that 3D printed customized orthopedic implants are still officially restricted in use. Cai Hong expressed regret that, at the present, the model which got approved is only for mass production, while individual customization cannot be achieved as there are still some demands that could not be met. Customization and personalization solutions need the support of the relevant laws and regulations, he says, adding that he hopes that these 3D printed hip parts will act as promotional pieces within the drug administration system. ‘It is said that at the end of year, drafts on the individual customization of the medical devices regulations will be introduced for comment,’ he adds. That will hopefully bode very well for the future.